Pliers, which are hand-actuated tools used for installing retaining rings in holes, on shafts or axles and the like, are well known. These pliers usually comprise an actuating shank having a portion which extends beyond the joint as a tool shank terminating at its free end in projections which fit the retaining ring so that the tool shank can engage therein to expand or contract it. These projections are typically in the form of pins, for example, which engage in corresponding mounting holes on the free terminal ends of the horshoe-shaped retaining ring. In some instances, the tool shank of the pliers is offset or bent at an angle for ease of operation and also to provide a means for inserting retaining rings into bore openings or the like. However, if it is desired to assemble a retaining ring in a relatively deep hole or opening having a groove relatively far away from the edge of the opening, then it is necessary for the pliers to have tool shanks with a correspondingly long, bent portion. In this case, however, the tensioning capacity of the pliers is considerably reduced because the tool shanks must be bent sharply by reason of their considerable length. Even if it is possible to tension the retaining ring in the first place, there is considerable danger that it will slip from the projections. Furthermore, it is no longer possible to observe the orientation of the retaining ring in the opening so that snapping the ring into the intended groove is oftentime a time consuming process of trial and error.
To solve this problem, various types of tensioning devices have been proposed. For example, West German Utility Model No. 1,947,498 shows a mounting mandrel having clamping jaws which surround the retaining ring on all sides. These jaws contract radially around conical surfaces and release the retaining ring by means of an ejector which moves in an axial direction. Even though mounting positions which are located in very deep openings can be reached by this arrangement, it is impossible to monitor the snapping in of the retaining ring into its intended groove by reason of the fact that with this design there is no automatic feed-back from the position of the plier levers as there is with the conventional type of pliers indicating that the retaining ring is snapped into place.
With the foregoing in mind, it is an object of the present invention to provide pliers characterized by novel features of construction and arrangement whereby it is easy to introduce retaining rings even into mounting position which are relatively remote from the edge of an opening.
The present invention overcomes the drawbacks of the prior art and provides solution to the problems discussed above by reason of the fact that the device is designed as a sleeve bearing having considerable axial length wherein one of the tool shanks is connected to one of the actuating shanks by way of the sleeve and the other tool shank is connected to the other actuating shank by way of the shaft of the sleeve bearing. By this arrangement, it is possible to transmit the tensioning force advantageously in a rigid manner from the actuating shanks to the tool shanks even when the tool shanks are spaced a considerable distance from the actuating shanks. The sleeve bearing consists of a shaft and a sleeve which rotates on the shaft, both parts being subjected to torsion when the retaining ring is tensioned. In this fashion, the tool shanks are not subjected to any bending force and provide stable transmission elements for the tensioning forces which are at least equal to that of a compact pliers of known design. Further, the sleeve bearing can be made with a comparatively small diameter so that the pliers, in accordance with the present invention, are suitable for assembling retaining rings in bores of extremely small size. In accordance with the design of the present invention, it is possible to operate the actuating shanks either manually or by simple modification by automatic machine means.
In accordance with another feature of the present invention, the tool shanks are in the form of disks having axial projections which fit the retaining ring thereby to engage with it. At least one of the tool shanks may be provided with a radial support surface for the retaining ring which is preferably located diameterically opposite the axial projections. The disk-shaped configuration of the tool shanks provides a particularly stable and positionally rigid assembly facilitating tensioning of the retaining ring reliably without the danger of its slipping off. The particular configuration of the support surface provides significant advantages since the retaining ring rests on at least three points about its circumference. Accordingly, when it is being guided into an opening, it remains oriented in the desired radial direction required for it to be snapped securely into a groove.
In accordance with another feature of the present invention, the pliers are provided with a gauge device for indicating the installation position of the retaining ring. This gauging device may consist, for example, of a sensor which is located near the tool shank and which transmits a signal when the desired installation position for the retaining ring has been reached. Alternatively, it can be formed by a feeler which is free to move axially with respect to the tool shanks and which is supported elastically against them and runs against the end surface of the machine element to be secured. The sensing surface of the feeler may be formed by a disk with an outer diameter smaller than the bore diameter of the tensioned retaining ring and can be connected to a bolt which is free to move axially in the shaft and which, therefore, emerges near the actuating levers and in this fashion indicates the installation position. The gauge device facilitates easier location of the installation position and accordingly, installation is rendered highly efficient particularly in the case of grooves which are located at as great depth in the opening in a position where it is no longer possible to observe the ring being introduced. With the pliers according to the present invention, they are simply positioned into the opening until the gauge device generates a signal displayed in an external visible location. In this position, the tensioning force is reduced which causes the retaining ring to snap in place. In the very simple design with bolts, the end of the bolt emerges from the shaft when the disk near the tool shank is pushed in the axial direction. This happens when the disk with its front end sensing surface is pushed, for example, against the end surface of a machine part to be secured axially.
The sensor may comprise an electrical/electronic sensor with optical display. The lamp, for example, connected to a contact sensor or to a sensor operating electronically signals the proper installation position.